HTML Tidy 5.2.0
The HTACG Tidy HTML Project
Overview of popular features and problems
Indenting the source markup of an HTML document makes the markup easier to read. Tidy can indent the markup for an HTML document while recognizing elements whose contents should not be indented. In the example below, Tidy indents the output while preserving the formatting of the
Tidy’s indenting behavior is not perfect and can sometimes cause your output to be rendered by browsers in a different way than the input. You can avoid unexpected indenting-related rendering problems by setting
indent:auto in a config file.
Tidy defaults to assuming you want output to be encoded in
UTF-8. But Tidy offers you a choice of other character encodings:
ISO Latin-1, and the
ISO 2022 family of 7 bit encodings.
Tidy doesn’t yet recognize the use of the HTML
<meta> element for specifying the character encoding.
The full set of HTML character references are defined. Cleaned-up output uses named character references for characters when appropriate. Otherwise, characters outside the normal range are output as numeric character references.
Tidy offers advice on potential accessibility problems for people using non-graphical browsers.
Some tools generate HTML with presentational elements such as
<center>. Tidy’s -clean option will replace those elements with
<style> elements and CSS.
Some HTML documents rely on the presentational effects of
<p> start tags that are not followed by any content. Tidy deletes such
<p> tags (as well as any headings that don’t have content). So do not use
<p> tags simply for adding vertical whitespace; instead use CSS, or the
<br> element. However, note that Tidy won’t discard
<p> tags that are followed by any non-breaking space (that is, the
named character reference).
You can teach Tidy about new tags by declaring them in the configuration file, the syntax is:
The same tag can be defined as empty and as inline, or as empty and as block.
These declarations can be combined to define a new empty inline or empty block element, but you are not advised to declare tags as being both inline and block.
Note that the new tags can only appear where Tidy expects inline or block-level tags respectively. That means you can’t place new tags within the document head or other contexts with restricted content models.
Tidy will gracefully ignore many cases of PHP, ASP, and JSTE instructions within element content and as replacements for attributes, and preserve them as-is in output; for example:
But note that Tidy may report missing attributes when those are “hidden” within the PHP, ASP, or JSTE code. If you use PHP, ASP, or JSTE code to create a start tag, but place the end tag explicitly in the HTML markup, Tidy won’t be able to match them up, and will delete the end tag. In that case you are advised to make the start tag explicit and to use PHP, ASP, or JSTE code for just the attributes; for example:
Tidy can also get things wrong if the PHP, ASP, or JSTE code includes quotation marks; for example:
Tidy will see the quotation mark preceding ID as ending the attribute value, and proceed to complain about what follows.
Tidy allows you to control whether line wrapping on spaces within PHP, ASP, and JSTE instructions is enabled; see the
wrap-jste config options.
Tidy can help you to correct well-formedness errors in XML markup. Tidy doesn’t yet recognize all XML features, though; for example, it doesn’t understand CDATA sections or DTD subsets.